Asha commands her own ship. Her men listen to her and obey her, and do not regard her brother Theon with the same respect. Since Theon was under the wing of House Stark for most of his life, she was raised as the Greyjoy heir.

In A Clash of Kings, Theon returns to The Iron Islands. Asha wants to know how time has changed Theon, so she flirts with him, pretending to be a Esgrid a shipwright's wife. When he later learns she's his sister, he is furious with her, and even angrier that their father favors her. She goes to Theon after he takes Winterfell, in answer to his calls for more men, but only brings him 10 men to help him keep the castle. She has come primarily to get him to leave Winterfell, as the castle is too far from the sea for them to enforce or supply. However, she cannot get Theon to abandon his prize.

In The Winds of Winter, she tries to get Stannis Baratheon to set her and Theon free, but he demands that Theon be killed for his actions against the Starks. She requests he be killed by beheading because she knows the other option is being burned alive, which is a more painful death.